1. Field of the Invention
The present invention relates to a printer with a paper aligning device for aligning a recording paper with a paper transport path in the printer.
2. Background Arts
There have been such printers and photocopiers that is provided with a paper aligning device for aligning a recording paper on a paper transport path through the apparatus. The paper aligning device corrects the position of the conveyed recording paper if it the recording paper is on the skew relative to the paper transport path or deviates from a center of the paper transport path.
An exemplary of paper aligning device is disclosed in Japanese Laid-open Patent Application No. 8-143183, wherein a leading end of the recording paper is pressed against a pair of feed rolls for correcting the skewed recording paper and, at the same time, guide members are pressed onto opposite side edges of the recording paper for aligning the center of the recording paper with the center of the paper transport path.
Another type of paper aligning device is disclosed in Japanese Patent Publication No. 62-13248, wherein a stationary guide member is disposed on one lateral side of the paper transport path, and a movable guide member is disposed on the other lateral side of the paper transport path. The movable guide member is moved in a perpendicular direction to the transport path, to push one side edge of the conveyed recording paper such that the other side edge of the recording paper is pressed against the stationary guide member. Thereby the recording paper is aligned with the paper transport path.
However, these conventional types of paper aligning devices would cause a problem if they are applied to such a printer where a continuous web of recording paper is loaded in the form of a roll, and is cut at a length after an individual image is recorded thereon. The problem is that the recording paper can be distorted or twisted between the paper roll and the paper aligning device, and thus get bent or wrinkled.
The recording paper is distorted when the recording paper is limited in the lateral or widthwise direction thereof simultaneously at a plurality of points between the paper aligning device and the paper roll. For the sake of preventing the distortion, it has been found to be effective to provide a room for allowing the recording paper to form a loop between the paper aligning device and the paper roll, because the loop absorbs the distortion. But the recording paper could get jammed in the room for the loop while the recording paper is being fed into the paper transport path.
In view of the foregoing, an object of the present invention is to provide a printer with a paper aligning device, that prevents the distortion of the recording paper during the alignment and the printing operation.
A printer according to the present invention comprises: a paper supply section for supplying a recording paper therefrom; a feed roller pair for nipping and conveying the recording paper along a paper transport path; a printing head for printing an image on the recording paper in synchronism with conveying movement of the recording paper; an aligning device disposed in the paper transport path between the paper supply section and the printing head, the aligning device pushing side edges of the recording paper in a lateral direction to the paper transport path to align the recording paper with the paper transport path; and a path size switching device disposed between the paper supply section and the aligning device, the path size switching device being switched to a limiting position while the recording paper is being conveyed in a paper supply direction from the paper supply section toward the printing head, for limiting the paper transport path in a direction of thickness of the recording paper, and to a widening position while the aligning device is being activated and while the recording paper is being conveyed in a reverse direction to the paper supply direction, for widening the paper transport path in the direction of thickness of the recording paper and allowing the recording paper to make a loop between the paper supply section and the aligning device.
The loop absorbs torsion applied to the recording paper between the paper supply section and the aligning device where the recording paper is skewed before being aligned by the aligning device.
According to a preferred embodiment, the paper transport path of the printer of the present invention has a vertical transport path section between the paper supply section and the aligning device, and the path size switching device is provided in the vertical transport path section.
It is preferable to gently curve the paper transport path in a section passing through the aligning device. Since the stiffness and rigidity of the recording paper is increased in the curved portion, the recording paper is prevented from being bent or folded by the pressure applied to the side edges from the aligning device.